getlocal.go

func getLocalAddr(machines []string) (string, error) {

 for _, m := range machines {
  conn, err := net.Dial("udp", m)
  if err != nil {
   continue
  }
  defer conn.Close()

  return strings.Split(conn.LocalAddr().String(), ":")[0], nil
 }
 return "", errors.New("no reachable machine to get local addr")
}